According to data published in the European Journal of Clinical Nutrition, intakes greater than 500 International Units (IU) per day were associated with a 13 percent reduction in the risk of type-2 diabetes.
Researchers from Tufts Medical Center and Carney Hospital in Massachusetts also report that people with the highest blood levels of vitamin D, measured as more than 25 nanograms per milliliter, had a 43 percent lower risk of developing type-2 diabetes than people with the lowest blood levels (less than 14 ng/ml).
The results are based on a meta-analysis of eight observational cohort studies and 11 randomized controlled trials measuring vitamin D and diabetes.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
The link between vitamin D and metabolic syndrome is plausible biologically. Vitamin D deficiency has previously been linked to impaired insulin secretion in animals and humans, and has also been linked to insulin resistance in healthy, glucose-tolerant subjects.
“Vitamin D may play a role in type 2 diabetes; however, to better define the role of vitamin D in the development and progression of type 2 diabetes, high-quality observational studies and RCTs that measure blood 25-hydroxyvitamin D concentration and clinically relevant glycemic outcomes are needed,” wrote the researchers, led by Tufts’ Anastassios Pittas, an adjunct associate professor at the Friedman School of Nutrition Science and Policy.
According to the World Health Organisation (WHO), diabetes affects over 220 million people globally and the consequences of high blood sugar kill 3.4 million every year. If such statistics weren’t scary enough, the WHO is predicting deaths to double between 2005 and 2030.
The total costs associated with the condition in the US alone are thought to be as much as $174 billion, with $116 billion being direct costs from medication, according to 2005-2007 American Diabetes Association figures.
Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 diabetes.
Source: European Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1038/ejcn.2011.118
“Vitamin D and type 2 diabetes: a systematic review”
Authors: J. Mitri, M.D. Muraru, A.G. Pittas